Does anybody know, is it possible to install a mix of avast! Endpoint Protection and avast! Endpoint Protection Suite under SOA or EA, like avast! Professional and avast! Standard Suite under ADNM in the past ?
NO, you cannot combine avast! Endpoint Protection licenses with avast! Endpoint Protection Suite licenses under the same console.
You need, at least, two consoles, one per licensed product. 
To reseller’s (and avast! itself) regret… With v. 4.8, it was possible to offer very affordable configuration to the clients, Standard Suite and Professional under the same ADNM.
I have found that the price has stayed about the same (or much less in many cases), as I renew my 4.8 clients to Endpoint Protection Suite.
20 user 4.8 = 10 Std Suite @ $419.50 + 10 Pro @ $249.50 = $669.00 - 30% renewal = $468.30
20 user Endpoint Protection Suite = $619.80 - 30% renewal = $433.86
The cost is cheaper, and therefore, the resellers now make less money that before!
A similar question: Is it possible to combine Endpoint Protection and Email Server Security in one console?
No, avast! Email Server Security is a unmanaged product, you need avast! Endpoint Protection Suite Plus.